The present invention relates to a method of subdividing stacks of superimposed layers, such as paper sheets, into smaller stacks or piles. More particularly, the invention relates to improvements in a method of subdividing a series of successive stacks into smaller stacks or piles by resort to a substantially wedge-like or sword-like tool, e.g., a tool of the type disclosed in my commonly owned U.S. Pat. No. 4,313,703 granted Feb. 2, 1982 for "Apparatus for breaking up stacks of paper sheets or the like". The disclosure of this patent is incorporated herein by reference.
My aforesaid patent discloses an apparatus wherein the stack which is to be divided into two or more smaller stacks or piles is held between the jaws of a tongs in such a way that the reciprocable tool can penetrate into one edge face of the stack. The patented apparatus further comprises an adjustable eccentric cam which can select the position of the tongs with reference to the path of movement of the tool to thus vary the number of sheets in the piles which are obtained on penetration of the tool into the edge face of the stack between the jaws of the tongs. Once the tool has penetrated into the stack, the resulting piles are removed one after the other.
Adjustability of the tongs with reference to the path of movement of the tool is desirable, even if the number of sheets or layers in successive stacks of a short or long series of stacks is constant, because this does not always and invariably ensure that successive stacks will be broken up into piles of identical height or into piles containing identical numbers of layers or sheets. This is due to the fact that the thickness of layers or sheets in successive stacks can vary within a given (and often very wide) range. In order to counteract the effect of varying thickness of layers or sheets upon the thicknesses or height of piles, it was already proposed to carry out an additional dividing operation. The apparatus of my aforementioned patent is constructed and assembled in such a way that the additional dividing operation or step can be dispensed with by providing means for lowering the last pile of a freshly divided stack prior to removal from the tongs so that the tool is invariably free to advance to a level above the topmost layer or sheet of the last pile. Such apparatus has found widespread acceptance in the paper processing industries in spite of the fact that it cannot always ensure the subdivision of successive stacks into piles of predetermined thickness. On the other hand, it is often desirable or necessary to guarantee that the number of layers or sheets in each of the piles which are obtained on subdivision of a stack will be the same. As a rule, the last pile of a stack which is treated in the patented apparatus will contain a number of layers or sheets which deviates, often appreciably, from the number of layers in the other pile or piles of the same stack. Such deviations are not always acceptable, e.g., when the stacks must be broken up into piles each of which should contain a fixed number of layers or sheets prior to conversion of piles into note books, steno pads, exercise books or like stationery products having numbered pages whose total number must or should match a given value.